Vapochromic materials suitable for sensing volatile organic compounds (VOCs) by the alteration of auro- and metallophilic attractions have attracted considerable attention. Whereas these systems often include metallophilic Pt—Pt, Au—Tl, Au—Au, and Au—Ag interactions, complexes with Au—Cu metal centers are generally less common, and such vapochromic complexes are understood to have not been reported.
The mechanism associated with the vapochromic response typically involves reversible rearrangements catalyzed by solvent vapor or interstitial solvation of transition metal complexes. Additionally, solid-vapor reactions involving the exchange of ligands coordinated to metal centers are quite rare. However, solvents are known to reversibly replace H2O at Fe centers and Co centers of certain solid state metal complexes, and HCl(g) has been observed to add reversibly to [CuCl2L2] (L=3-chloropyridine, 3-bromopyridine) and thereby afford [HL]2(CuCl4). Further, the viability of ligand exchange in metal complex polymers of the general formula [CuLn](Au(CN)2)2 utilizing solvent vapors with different functional groups has been disclosed in U.S. Patent Application Publication No. 2009/0130768.
Vapochromic materials have recently been incorporated in chemical sensor devices. For example, [Au—(PPh2C(CSSAuC6F5)PPh2Me)2][ClO4] has been used in the development of an optical fiber VOC sensor. A vapochromic light emitting diode and a vapochromic photodiode have also been built using tetrakis(p-dodecylphenylisocyano) platinum tetranitroplatinate and bis(cyanide)-bis(p-dodecylphenylisocyanide)platinum(II), respectively.
Despite the foregoing, a need exists for new vapochromic materials that may be suitable for use in chemical sensor devices, such as VOC sensors.